Bought a Mad Catz RAT M mouse to work with my late model 2013 15" MBP 10.9.2 and it's going back to the store. Great construction and design but the Bluetooth 4.0 simply doesn't stay connected for more than a few seconds at a time. I also tried it on another MBP sans their driver (which also doesn't recognize the mouse even though it's for 10.9). I've tried restating SMC & PRAM, deleting the bluetooth.plist file etc, etc... I'm not going to use their Bluetooth dongle so that's out. I do have a 2013 Razor Orochi and it's had zero Bluetooth issues but the buttons were starting to fail and the battery life isn't very long (maybe 30hrs usage on 2500mAh NiMH AA cells), and it sleeps in only a couple of minutes of idling. The RAT M claims up to a year on two AAA cells, nice if it actually worked with my MBP. The good, well lots of buttons, great build quality and ergonomics.